Replace wrong PDF non-latin characters

I can use many operating systems, many applications, many programming languages.
But the best language for me is C# .NET. I can learn to use any application.
PDF files often are created with problem : non-latin characters are displayed but do not exist. Let's say : Ž is displayed correctly but then copied is shown incorrectly.
I open PDF file with 'Foxit Reader' Windows, 'Goodreader' iOS. You can copy text anywhere with copy-paste function.
I don't have original file(txt, word) from which PDF was created.
The problem is font : somebody created PDF with wrong font which does not accept non-latin characters. The problem started from wrong font in PDF.
Wrong font name : WtUStoneSerItcTMed7qREumM

Times New Roman accept non-latin characters but I cannot change font for whole PDF. I've tried to change it to Times New Roman for whole PDF page - disaster.
I can only change font for very exact letters with command 'Replace All' Ctrl+H.

I need to have correct non-latin characters so that I could search any word within every page of PDF :
All incorrect symbols :
I am able to fix these wrong letters with 'Foxit Advanced PDF Editor'. However, I am not able to fix these wrong characters with 'Foxit Advanced PDF Editor' then they are at the beginning of paragraph(wildcards are not working for whatever the reason is) :
But I am not able to fix these :I need to replace incorrect symbols into correct symbols. What other PDF editor applications, systems, etc. do you suggest ?
Here's how I work with "Foxit advanced PDF Editor" :
Thanks

No, you just need the fonts.
From what I see, you need ITC Stone Serif and the other one I don't recognize.
Try to replace it with a font that you know supports those characters, since you don't really care about appearance.

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Adobe software is even worse.
The thing that I've noticed : the problem may be not within software but with Operational system and it's installed fonts.
I've found that with foxit reader(not editor) it is possible to find these letters :But Foxit Reader is not meant for editing PDF file.
'Foxit Advanced PDF Editor' : no possibility of finding above letters.

After working a bit on the file, I can tell you that it's not you, it's the file: the Unicode map is corrupt.
See here for an explanation and here for a possible solution: convert the pdf to curves (so all text info is removed) then OCR it.

That's the right path. I see that there are several settings for conversion to curves and OCR file.
Could You give exact instructions ? I don't care which software to use. Also, acrobat 9 is different from 11 pro. For whatever software You suggest - also, which software version do You suggest ?

I have tried before converting whole document to tiff files and OCR with ABBYY finereader pro 11. That is working but I need better ways. The problem is always : no bold text for some letters(in original some letters are bold). Every page in ABBYY has the same problem.

Of course, if there is a better a way to OCR file - I need EXACT instructions.

There are improvements but another problems :)
Is there a workaround without OCR ? We all know that OCR always produce errors.
Foxit Advanced PDF Editor did fix some Lithuanian letters. Even if I would install right fonts - would PDF editor software still not find these letters ?
Another OCR problems :

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